Step 1: The parents install electronically-controlled gates against the threat from the outside world.
The family in the short story already have insurance, a fenced-in swimming pool, e.t.c, choose to install electronically-controlled gates as their initial care against the threat from outside.
Step 2: The parents install burglar bars on the doors and windows and an alarm system.
The maid begs the family to install burglar bars on the doors and windows and an alarm system, which occurs after the maid is bound up while burglars steal every property from the family's home.
Step 3: The parents raise the wall. They also add razor-bladed coils.
They raised the bar. However, the view of the cat climbing the wall means the family still does not feel safe, so they install razor wire: "razor-bladed coils."